Dense Non-aqueous Phase Liquid Removal Research Articles

Ebullition-facilitated mobilization of trapped dense non-aqueous phase liquid at residual saturation from sandy sediments.

Gas ebullition can mobilize dense non-aqueous phase liquids (DNAPLs) from sediments to the overlying water column, increasing the DNAPL-impacted area and posing serious challenges to the remediation and management of contaminated sediments. Despite this, there have been few laboratory studies focused on gas ebullition-facilitated transport of DNAPL. In this study, bubble-facilitated transport was investigated by injecting gas (air or nitrogen) at 1mL/min through a creosote source zone (∼25% saturation) capped with sand layers of different thicknesses. Three short-term experiments (8.3-8.7h) were capped with 11.4, 7.0 or 4.5cm of sand to estimate DNAPL flux. One long-term experiment (30 days) was capped with 8cm of sand to investigate DNAPL removal. Heptane placed on a layer of water above the sand was used as a solvent trap and analyzed for petroleum hydrocarbons (PHCs). Results showed that creosote travelled as thin coatings and films surrounding gas bubbles migrating out of the source zone. Gas invasion was dominated by capillarity in the 11.4cm-thick sand layer and by fracturing in the 7.0 and 4.5cm-thick sand layers. Migration through these fractures often led to the formation of creosote tails on mobilized bubbles that drained towards the rear end of the bubble. The mass released decreased exponentially with sand cap thickness. In the long-term experiment, images showed significant depletion of the source zone in 30 days. Linear regression analysis showed that relationships with high predictive capabilities for ebullition-facilitated fluxes of hydrophobic organic contaminants can be obtained by incorporating gas ebullition flux and source strength, based on results from this study along with others from the field and laboratory. To our knowledge, this is the first study to compile and integrate data collected from laboratory and field studies to develop an assessment tool to facilitate the management of contaminated sediments affected by gas ebullition.

Evaluation of alkaline activated sodium persulfate sustained release rod for the removal of dissolved trichloroethylene

The presence of trichloroethylene (TCE) dense non-aqueous phase liquid (DNAPL) in the subsurface can generate a dissolved phase plume in groundwater. This study developed an alkaline activated sodium persulfate (SPS) sustained release oxidation rod (alkaline SPS SR-Rod) for long-term in situ chemical oxidation accelerated treatment of TCE dissolved from TCE DNAPL, by creating a greater concentration gradient at the TCE DNPL boundary. The dissolution of TCE DNAPL (1 mL) in water (280 mL) generated ~700 mg L−1, with a volumetric mass transfer coefficient (kLa) of 0.0187 d−1. The alkaline SPS SR-Rod system had a kLa of 0.013 d−1 for TCE dissolution at early stage, and thereafter aqueous TCE concentration remained below ~10 mg L−1 over 60 d of reaction. An SPS SR-Rod life-span of 186 d, for 90% of SPS released from the rod, was estimated. In the soil-water system, aqueous TCE was maintained < 3 mg L− 1 throughout the reaction and the soil oxidant demand was determined to be ~4 g-SPS/kg-soil in the alkaline SPS SR-Rod system. These results revealed that the use of the alkaline SPS SR-Rod can be effective as a method of treating dissolved TCE released from DNAPL contamination, and thereby accelerating TCE DNAPL removal.

Enhanced-solubilization and dissolution of multicomponent DNAPL from homogeneous porous media

The presence of multicomponent dense nonaqueous phase liquid (DNAPL) mixtures in porous media can significantly limit the effectiveness of groundwater remediation. A series of column transport and flushing experiments were conducted to quantify the impact of various enhanced flushing agents on dissolution and removal of a multicomponent DNAPL source within a macroscopically homogeneous porous medium. The columns were established with NAPL saturations consisting of an equal mole mixture of cis-1,2-dichloroethene, trichloroethene, and tetrachloroethene. The solubilization agents used included two complexing sugars - hydroxypropyl-β-cyclodextrin (HPCD and methyl-β-cyclodextrin (MCD); a surfactant - sodium dodecyl sulfate (SDS); and a cosolvent - ethanol (EtOH). The chemical flushing agents greatly reduced the time needed to remove each DNAPL component, compared to flushing with water alone. Initial DNAPL-component elution concentrations were successfully predicted using Raoult's Law for MCD, HPCD, and water flushing, indicating that ideal dissolution was initiated by the lower-power enhanced-solubilization agents. EtOH was most efficient at removing the contaminants in terms of normalized mass recovery but least efficient based on a mass-ratio and mole-ratio of contaminant to reagent analysis. SDS was most efficient for contaminant removal when analyzed based on mass-contaminant to mass-reagent recovered and MCD was most effective based on a moles-contaminant to moles-reagent recovered efficiency evaluation. However, in terms of mass flux reduction analysis (i.e. removal metric), SDS was least efficient for contaminant removal compared to all other enhanced-flushing agents tested, especially during the initial stages of DNAPL removal. Results from this study indicate that ideal dissolution was initiated during enhanced-solubilization and that several criteria should be used to evaluate the removal effectiveness of flushing agents for multi-component NAPL systems.

Enhancing DNAPL removal from low permeability zone using electrical resistance heating with pulsed direct current

Electrical resistance heating (ERH) has been widely applied for contaminant remediation in heterogeneous sites especially when low permeability zones exist, yet requires high energy input. To address the low energy-efficiency of ERH using conventional alternating current (AC), pulsed direct current (PDC) obtained by current rectification was introduced for heating to enhance dense nonaqueous phase liquid (DNAPL) migration in low permeability zones. Here we showed the proof-of-concept in a lab-scale two-dimensional heterogeneous sand system (40 cm × 30 cm) with trichloroethylene (TCE) DNAPL in the central low permeability zone. Applying PDC achieved faster temperature increase compared to that with the conventional AC of the same voltage gradient. The overall TCE removal efficiency from the cell increased from 79.0% to 89.6% with increasing PDC voltage gradient from 3 to 3.75 V cm–1, compared to that of 9.4–91.1% with conventional AC. The lowest energy consumption of PDC was 390 kWh kg–1 at a medium voltage gradient of 3.5 V cm–1, which was 27.8% lower compared to that with AC at the same voltage gradient. These results suggest that remediation using pulsed direct current is a promising approach to improve the energy-efficiency and effectiveness of ERH.

Experimental investigation of cosolvent flushing of DNAPL in double-porosity soil using light transmission visualization

This paper investigates the effect of cosolvent content and flushing velocity on the remediation of dense non-aqueous phase liquid (DNAPL) in double-porosity medium using light transmission visualization technique (LTV). Double-porosity was created using local silica sand and sintered spheres of kaolin, arranged in a periodic manner. The flushing solution consisted of ethanol–water mixtures with various ethanol concentrations ranging from 20% to 65% by volume. The effect of contact time was investigated by changing the flow rates of the flushing solution. The accuracy of the LTV technique was examined by comparing an actual injected volume of DNAPL with the calculated volumes generated from image analysis. The LTV results allowed for the visualization of the DNAPL enhanced dissolution as well as its mobilization. While the removal efficiency increased with the increase of the ethanol content, the removal efficiency was negatively affected by the velocity of flushing solution. Image analysis revealed that the highest DNAPL removal efficiency of 92% was obtained at 65% ethanol content and low flushing velocity. This efficiency decreased to 85%, in the case of high flushing velocity. Overall, this study demonstrated that the LTV technique is a viable laboratory tool that can accurately depict enhanced DNAPL dissolution and DNAPL mobilization due to cosolvent flushing.

A stochastic optimization model based on adaptive feedback correction process and surrogate model uncertainty for DNAPL-contaminated groundwater remediation design

A stochastic optimization model based on an adaptive feedback correction process and surrogate model uncertainty was proposed and applied for remediation strategy design at a dense non-aqueous phase liquids (DNAPL)-contaminated groundwater site. One hundred initial training samples were obtained using the Latin hypercube sampling method. A surrogate model of a multiphase flow simulation model was constructed based on these samples employing the self-adaptive particle swarm optimization kriging (SAPSOKRG) method. An optimization model was built, using the SAPSOKRG surrogate model as a constraint. Then, an adaptive feedback correction process was designed and applied to iteratively update the training samples, surrogate model, and optimization model. Results showed that the training samples, the surrogate model, and the optimization model were effectively ameliorated. However, the surrogate model is an approximation of the simulation model, and some degree of uncertainty exists even though the surrogate model was ameliorated. Therefore, residuals between the surrogate model and the simulation model were calculated, and an uncertainty analysis was conducted. Based on the uncertainty analysis results, a stochastic optimization model was constructed and solved to obtain optimal remediation strategies at different confidence levels (60, 70, 80, 90, 95%) and under different remediation objectives (average DNAPL removal rate ≥ 70, ≥ 75, ≥ 80, ≥ 85, ≥ 90%). The optimization results demonstrated that the higher the confidence level and remediation objective, the more expensive was remediation. Therefore, decision makers can weigh remediation costs, confidence levels, and remediation objectives to make an informed choice. This also allows decision makers to determine the reliability of a selected strategy and provides a new tool for DNAPL-contaminated groundwater remediation design.

Surfactant foam flushing for in situ removal of DNAPLs in shallow soils

An innovative process combining surfactant foam and surfactant flushing (SF) for the remediation of a shallow saturated soil contaminated with a dense non-aqueous phase liquid (DNAPL) residual was investigated at bench-scale. First, foam was formed by injecting DHSS surfactant and nitrogen in alternation in soil (SAG process) at constant pressure. The effect of pressure gradients set point (≤90kPam−1) on DNAPL recovery was investigated. Foam front mobilized DNAPL with a piston-like fast propagation (1.8md−1) despite the low pressure gradients. 34–60% of DNAPL residual was extracted with low surfactant consumption (<0.4kgkg−1 DNAPL removed). Then, a solubilizing agent (Tergitol) was injected into soil, previously treated with foam, to improve the DNAPL removal. It led a removal up to 95% whereas only 2 porous volume (PV) of solubilizing solution were injected. As a comparison, when the solubilizing agent was injected without foam pre-treatment, 40 PV would have been required to lead the removal up to 90%. Considering the overall treatment, the technology we developed requires 10-times less surfactant than the traditional SF technology. This technology is especially suitable for very shallow soils where injection pressure has to be kept at a low level to avoid soil heaving.

Steam-Enhanced Extraction Experiments, Simulations and Field Studies for Dense Non-Aqueous Phase Liquid Removal: A Review

Experiments, simulations and field studies for dense non-aqueous phase liquid (DNAPL) removal have demonstrated successful recovery through steam-enhanced extraction. Steam-enhanced extraction is an innovative technology for soil and groundwater remediation to remove as much contamination as possible. Most of researchers study the main DNAPL recovery mechanisms such as physical displacement by vaporization, evaporation and condensation, reduction in interfacial tension and DNAPL viscosity influenced by temperature. Other removal mechanism such as steam distillation and steam stripping also has been studied. The removal of DNAPL using steam-enhanced extraction shall be investigated to identify, acquire, analyze, visualize, and evaluate the effectiveness of the remediation. Several parameters can be controlled to justify the successful of the remediation. A comprehensive understanding of the subsurface environment, multiphase fluid flow and the physical processes is required to prevent remediation failure. Thus, it will avoid continuous contamination of the subsurface environment. The researcher can quantify the reduction in contamination remediation and acquire high quality data sets to validate future numerical model. Aim of this paper is to review and to summarize the existing laboratory experiment, simulations and field studies from other researchers regarding steam-enhanced extraction for dense non-aqueous phase liquid removal.

Factors affecting gas migration and contaminant redistribution in heterogeneous porous media subject to electrical resistance heating

A series of intermediate-scale laboratory experiments were completed in a two-dimensional flow cell to investigate gas production and migration during the application of electrical resistance heating (ERH) for the removal of dense non-aqueous phase liquids (DNAPLs). Experiments consisted of heating water in homogeneous silica sand and heating 270mL of trichloroethene (TCE) and chloroform (CF) DNAPL pools in heterogeneous silica sands, both under flowing groundwater conditions. Spatial and temporal distributions of temperature were measured using thermocouples and observations of gas production and migration were collected using front-face image capture throughout the experiments. Post-treatment soil samples were collected and analyzed to assess DNAPL removal. Results of experiments performed in homogeneous sand subject to different groundwater flow rates showed that high groundwater velocities can limit subsurface heating rates. In the DNAPL pool experiments, temperatures increased to achieve DNAPL–water co-boiling, creating estimated gas volumes of 131 and 114L that originated from the TCE and CF pools, respectively. Produced gas migrated vertically, entered a coarse sand lens and subsequently migrated laterally beneath an overlying capillary barrier to outside the heated treatment zone where 31–56% of the original DNAPL condensed back into a DNAPL phase. These findings demonstrate that layered heterogeneity can potentially facilitate the transport of contaminants outside the treatment zone by mobilization and condensation of gas phases during ERH applications. This underscores the need for vapor phase recovery and/or control mechanisms below the water table during application of ERH in heterogeneous porous media during the co-boiling stage, which occurs prior to reaching the boiling point of water.

DNAPL accumulation in wells and DNAPL recovery from wells: Model development and application to a laboratory study

Dense nonaqueous phase liquid (DNAPL) accumulation and recovery from wells cannot be accurately modeled through typical pressure or flux boundary conditions due to gravity segregation of water and DNAPL in the wellbore, the effects of wellbore storage, and variations of wellbore inflow and outflow rates with depth, particularly in heterogeneous formations. A discrete wellbore formulation is presented for numerical modeling of DNAPL accumulation in observation wells and DNAPL removal from recovery wells. The formulation includes fluid segregation, changing water and DNAPL levels in the well and the corresponding changes in fluid storage in the wellbore. The method was added to a three-dimensional finite difference model (CompSim) for three phase (water, gas, DNAPL) flow. The model predictions are compared to three-dimensional pilot scale experiments of DNAPL (benzyl alcohol) infiltration, redistribution, recovery, and water flushing. Model predictions match experimental results well, indicating the appropriateness of the model formulation. Characterization of mixing in the extraction well is important for predicting removal of highly soluble organic compounds like benzyl alcohol. A sensitivity analysis shows that the incorporation of hysteresis is critical for accurate prediction. Among the multiphase flow and transport parameters required for modeling, results are most sensitive to soil intrinsic permeability.

Surfactant foam technology for in situ removal of heavy chlorinated compounds-DNAPLs

The use of surfactant foam for the remediation of a saturated soil contaminated with a dense non-aqueous phase liquid (DNAPL) was investigated at bench-scale. Despite the presence of the DNAPL, high foam stability was obtained for a mixture of cocamidopropyl betaïne and dodecylsulfate at 0.05%. Foams were assessed in different injection conditions and were compared to commonly used remediation methods. Strong foams improved significantly the DNAPL recovery yield, which amounted up to 98%, owing to the propagation of a flat foam front, with low dissolution (<0.5gl−1) and surfactant consumption (<10gkg−1 DNAPL recovered). The effects of important parameters (gas to liquid ratio, injection velocity, gas nature) and methods for foam production on pressure gradient (∇P), remediation efficiency and surfactant consumption were investigated. Even for low injection velocities (4×10−4ms−1), capillary numbers were high enough (∼8×10−3) to push the DNAPL efficiently. DNAPL lowered ∇P for foam propagation because of its destabilising effect. The use of CO2 as gas reduced the ∇Ps for foam propagation by 35%. ∇P were also decreased by 25% for gas to liquid ratios lower than 75%, whereas, DNAPL removal remained high. This technology should lower spreading risks and treatment costs.

Optimization design based on ensemble surrogate models for DNAPLs-contaminated groundwater remediation

The optimization design of surfactant-enhanced aquifer remediation for dense non-aqueous phase liquids (DNAPLs)-contaminated groundwater is proposed through integrating simulation and optimization models. Many studies have demonstrated that the surrogate model is an effective tool for building a bridge between simulation and optimization models. In this paper, the simulation model was first established to simulate a surfactant-enhanced aquifer remediation process, and on this basis, the ensemble surrogate models were constructed by applying the polynomial regression model, radial basis function neurons network and Kriging surrogate models. Second, the best surrogate model was selected in terms of the three performance indices. Lastly, a non-linear programming optimization model was constructed with the target of minimizing the DNAPLs-contaminated aquifer remediation cost. Meanwhile, the best surrogate model was embedded into the optimization model as a constrained condition, and it was used to reflect the non-linear complex relationship between injection and extraction rates with DNAPLs removal rates instead of simulation models. The results showed that the ensemble surrogate models improved the performance of the single surrogate models. Moreover, ensemble surrogate models improved the computational efficiency, and the optimal strategies have been proved to be an effective guide for contaminant remediation processes.

Investigation and Remedial Approach Development for a TCE Spill Site: A Case Study

A trichloroethene (TCE) plume has been discovered inside an industrial park located in Taiwan. The objectives of this study were to characterize the solvent spill site and prepare a corrective action plan (CAP) for site remediation. The following tasks have been performed under Taiwan Soil and Groundwater Remediation Act corrective action: (1) geophysical survey to verify the existence and fate of all potential contaminant sources in the vicinity of the avionics repair shop; (2) soil-gas survey and soil/groundwater analyses to delineate the lateral and vertical extent of contaminants in the subsurface; (3) application of field screening techniques to determine the presence of dense, non-aqueous-phase liquids (DNAPLs); (4) contaminant transport modeling; (5) evaluation of the remedial options, conduction of cost analysis, and selection of the optimal treatment system. Results from the site characterization indicate that an extended TCE plume existed in site groundwater, which needs to be contained and remediated. A two-phase remedial approach has been developed. Phase I was to contain the existing dissolved groundwater plume in the surficial aquifer and initiate mass removal of DNAPLs. Phase II was to conduct feasibility studies and possibly test surfactant washing and biobarrier techniques.

Removal of trichloroethylene DNAPL trapped in porous media using nanoscale zerovalent iron and bimetallic nanoparticles: Direct observation and quantification

Direct trichloroethylene (TCE) dense non-aqueous phase liquid (DNAPL) removal inside pore areas using nanoscale zerovalent iron (NZVI) and bimetallic nanoparticles were first investigated in a water-saturated porous glass micromodel. Effects of nitrate, aqueous ethanol co-solvent, humic substance, and elapsed time on TCE DNAPL removal using NZVI were studied by direct visualization. The removal efficiency was then quantified by directly measuring the remaining TCE DNAPL blobs area using an image analyzer. As ethanol content of co-solvent increased, TCE DNAPL removal by NZVI was also increased implying sequential TCE DNAPL removal mechanisms: as dissolved TCE was degraded by NZVI, TCE dissolution from TCE blobs would be then facilitated and the TCE blob areas would be eventually reduced. The presence of nitrate and humic substance hindered the NZVI reactivity for the TCE DNAPL removal. In contrast, the TCE DNAPL removal efficiency was enhanced using bimetallic nanoparticles in a short-term reaction by generating atomic hydrogen for catalytic hydro-dechlorination. However, all TCE DNAPL removal efficiencies reached the same level after long-term reaction using both NZVI and bimetallic nanoparticles. Direct TCE DNAPL observation clearly implied that TCE blobs existed for long time even though all TCE blobs were fully exposed to NZVI and bimetallic nanoparticles.

Coupling surfactants/cosolvents with oxidants for enhanced DNAPL removal: A review

AbstractSurfactants and cosolvents are useful for enhancing the apparent solubility of dense nonaqueous‐phase liquid (DNAPL) compounds during surfactant‐enhanced aquifer remediation (SEAR). In situ chemical oxidation (ISCO) with permanganate, persulfate, and catalyzed hydrogen peroxide has proven to be a cost‐effective and viable remediation technology for the treatment of a wide range of organic contaminants. Coupling compatible remedial technologies either concurrently or sequentially in a treatment train is an emerging concept for more effective cleanup of DNAPL‐contaminated sites. Surfactants are effective for DNAPL mass removal but not useful for dissolved plume treatment. ISCO is effective for plume control and treatment but can be less effective in areas where large masses of DNAPL are present. Therefore, coupling SEAR with ISCO is a logical next step for source‐zone treatment. This article provides a critical review of peer‐reviewed scientific literature, nonreviewed professional journals, and conference proceedings where surfactants/cosolvents and oxidants have been utilized, either concurrently or sequentially, for DNAPL mass removal. © 2010 Wiley Periodicals, Inc.

A multi-objective optimization framework for surfactant-enhanced remediation of DNAPL contaminations

The occurrence of Dense Non-Aqueous Phase Liquid (DNAPL) contaminations in the subsurface is a threat for drinkwater resources in the western world. Surfactant-Enhanced Aquifer Remediation (SEAR) is widely considered as one of the most promising techniques to remediate DNAPL contaminations in-situ, be it with considerable additional costs compared to classical pump-and-treat remediations. A cost-effective design of the remediation set-up is therefore essential. In this work, a pilot SEAR test is executed at a DNAPL contaminated site in Belgium in order to collect data for the calibration of a multi-phase multi-component model. The calibrated model is used to assess a series of scenario-analyses for the full-scale remediation of the site. The remediation variables that were varied were the injection and extraction rate, the injection and extraction duration, and the surfactant injection concentrations. A constrained multi-objective optimization of the model was applied to obtain a Pareto set of optimal remediation strategies with different weights for the two objectives of the remediation: (i) the maximal removal of DNAPL and (ii) a total minimal cost. These Pareto curves can help decision makers to select an optimal remediation strategy in terms of cost and remediation efficiency. The Pareto front shows a considerable trade-off between the total remediation cost and the removed DNAPL mass.

Characterization and removal of DNAPL from sand and clay layered media

Important characterization and remediation techniques (e.g. partitioning tracer tests (PTT), cosolvent and surfactant flushing) have been developed over the years to deal with dense nonaqueous phase liquid (DNAPL) sources in the saturated zone. Unfortunately, subsurface media layering and heterogeneity pose a major challenge to the efficiency of these and other techniques that rely on flushing fluids through porous media. Using laboratory column experiments with both single media and layered-media columns and computer modeling of tracer breakthrough results, we examined the difficulty that layering poses to subsurface remediation and characterization techniques. Quantifying tetrachloroethylene (PCE) saturation in layered media was determined using PTT and effluent mass determinations. Conservative tracer breakthrough curves were used to determine permeability and the flow through layers before and after PCE contamination. The removal efficiency of alcohol flushing in the layered systems was also determined. Results showed that even a relatively simple layering with less than an order magnitude difference in permeability leads to difficulty in characterization and remediation using flushing technologies. These results suggest that much greater volumes of flushing solutions will be needed in heterogeneous environments to ensure adequate flushing of lower permeable lenses and layers.

Force analysis and visualization of NAPL removal during surfactant-related floods in a porous medium

Governing mechanisms of dense non-aqueous phase liquid (DNAPL) removal during surfactant and surfactant-foam (SF) flooding were studied by porous-patterned glass model experiments. Physical forces, viscous forces and capillary forces, acting on trichloroethylene (TCE) blobs were quantified to understand DNAPL removal mechanisms during the floods, simultaneously visualizing the removal mechanisms. The viscous force of the remedial fluid was intimately related to TCE removal from the porous medium. The remedial fluid with a high viscous force displaced more TCE blobs. Displacement of residual TCE by the remedial fluid began as viscous pressure of flooding was closed to the capillary pressure of the porous medium. In the region of viscous pressure less than the capillary pressure, residual TCE was either retained or solubilized, not displaced, implying that TCE solubilization was the dominant TCE removal process. Glass porous model visualization validated a dominance of the capillary forces during a surfactant flush and a dominance of the viscous forces of the displacing fluid during a SF flood.

Multi-Objective Optimization of the Setup of a Surfactant-Enhanced DNAPL Remediation

Surfactant-enhanced aquifer remediation (SEAR) is widely considered a promising technique to remediate dense nonaqueous phase liquid (DNAPL) contaminations in-situ. The costs of a SEAR remediation are important and depend mostly on the setup of the remediation. Costs can be associated with the installation of injection and extraction wells, the required time of the remediation (and thus labor costs, lease of installations, and energy), the extracted water volume (the purification of the extracted water), and the injected surfactant amount. A cost-effective design of the remediation setup allows an optimal use of resources. In this work, a SEAR remediation was simulated for a hypothetical typical DNAPL contamination. A constrained multi-objective optimization of the model was applied to obtain a Pareto set of optimal remediation strategies with different weights for the two objectives of the remediation: (i) the maximal removal of DNAPL mass (ii) with a minimal total cost. A relatively sharp Pareto front was found, showing a considerable tradeoff between DNAPL removal and total remediation costs. These Pareto curves can help decision makers select an optimal remediation strategy in terms of cost and remediation efficiency depending on external constraints such as the available budget and obligatory remediation goals.

Efficient, Near-Complete Removal of DNAPL from Three-Dimensional, Heterogeneous Porous Media Using a Novel Combination of Treatment Technologies

Remediation of porous media containing an entrapped dense nonaqueous phase liquid (DNAPL) is extremely difficult due to the heterogeneity and three-dimensional spatial nature of typical natural systems. A novel treatment technology based on surfactant- and gravity-induced mobilization, dense brine containment and collection, and a vapor-phase extraction polishing step is proposed as a means to remediate such systems. Laboratory experiments are performed using the suggested methodology applied to three-dimensional, heterogeneous systems, which are packed based upon a realization from a correlated random field. Entrapped DNAPL is effectively removed as a result of each component of the technology. Following vapor extraction, less than 1% of the original DNAPL mass remained in the system. While these results are very promising, several open issues must be resolved before this technology can be considered mature; both the investigation of some of these issues and a summary of remaining needs are addressed.